System of distribution.



No. 714,055. Patented Noma, |902'.

c. P. sTElNMETz.

SYSTEMUF DISTRIBUTION.

(Application tiled Mar. 6, 1899.) (No Mudgl.)

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CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SYSTEIVI OF DISTRIBUTION.

SPECIFICATION forming part of Letters Patent No. 714,055, dated November 18, 1902.

Application filed March 6, 1899.

To all la7/bont it may concern.-

Beit known that I, CHARLES P. STEINMETZ, a citizen of the United States, residing at Schenectady, county of Schenectady, State of 5 New York, have invented certain new and useful Improvements in Systems of Distribution, (Case No. 917,) of which the following is a specification.

In alternating-current systems of distibuxo tion for lighting purposes it is usually impracticable to employ a network` owing to the comparatively long distances between the installations of the various consumers. For this reason it is customary to supply each consumer or group of consumers with a transformer of a size `corresponding to the maximum load which may be put upon it. I find that even under the best conditions the load on such transformers is exceedingly variable, zo being practically nothing during the day-time and seldom reaching a maximum even in the evening. The core loss of the transformers therefore forms a comparatively large percentage of the energy supplied, and thus makes the all-day efficiency of the installation very low. Various means have been proposed for obviating the difliculties above mentioned, but so far as I am aware they are open to serious objections, either from a commercial or an engineering standpoint. In many-cases the transformers are operated from Sundown to midnight and disconnected during the remainder of the day. This has the obvious disadvantage that the circuits are dead at all other times than between sundown and midnight. Automatic devices have also been used for cutting in and cutting out transformers in various combinations unnecessary here to mention. These are expensive, 4o complicated, and unreliable.

My present invention aims to reduce the core loss of transformer installations without at the same time incurring the disadvantages above referred to and depends for its effectiveness upon the fact that in private dwelling-houses, stores, and the like by far the greatest number of lights or other translating devices'is needed in the evening, comparatively few lights being used during the day- Itherefore dividethe secondary wiring into two circuits, to one of which is connected Serial No. 707,879. (No model.)

all of those lights which are used only during the night-time and to the other the lights which are used during the day-time or during the day and night both. Each of these circuits is supplied from a transformer of asize corresponding to the maximum load on the circuit which it feeds. Instead of maintaining the secondary circuits distinct from each other I find it convenient to consolidate two 6o of the mains into a single conductor which acts as a common return for the currents carried by the two circuits, thus forming a species of three-wire system, which differs, how.- ever, from the ordinary Edison three-wire system as generally used in that the current in The common return is the sum and not the difference of the currents Howing in the outside mains. The primary windings of the transformers are similarly connected, the 7c three mains being carried back to the station. In one of the mains a switch isinserted, so as to cut out the night-transformer during the interval between midnight and the following sunset.

According to the arrangement above described the night-transformer is run at a comparatively high efficiency and is cut out of circuit while there is no call for current, thus saving a large amount of energy which would 8o otherwise be wasted in the transformer. The other transformer, which I term the allday transformer, is maintained in circuit day and night and being of small size dissipates but a small amount of energy, at the same time supplying the small demand for light in those places which require light both day and night-as, for instance, in cellars, vaults, and other dimly-lighted or unlighted places.

My invention furthermore comprises a system of multiple-rate metering to be used in connection with transformer installations of the character described, but which is also applicable, as will be readily understood, 95 to many other systems of distributing electricity. l n v The details of my invention will be fully described in the following specification, while its scope will be clearly and particularly rco pointed out in the appended claims.

Figure 1 illustrates diagram matically a system of distribution embodying my invention. Fig. 2 is a modification of the same.

Referring to Fig. l, G illustrates a source of alternating current-as, for instance, an

alternating-current generator. Three mainsa, b c lead therefrom, the mains a b being permanently connected to the terminals of the source G and the main c to one of the yterminals through a switch el of any suitable form. The all-day transformer D is connected across the mains a b, while the nighttransformer is connected across the mains h c. It will thus be observed that the all-day transformer D is always in circuit, while the night-transformer N may be cut in or out by operating the switch d. The secondaries of the transformers D and N are connected in series with terminals of like polarity together. From the common point between the secondaries and from the two remaining terminals are led the secondary mains A B C. Those lights or other translating devices which are to be used only at night are connected between the secondary mains of the night-transformer N, while the lights which are to be used or may be used at any time during the whole day of twenty-four hours are connected between the secondary mains of the all-day transformer D. The current which Iiows in the return-conductor B is the sum of the currents supplied to the translating devices at any one time.

It is generally possible to make the all-day transformer of very small sizue, thus saving an amount of energy almost equal to that which would be saved if a single large transformer were used during the night-time only and cutv out other times. In a transformer system of the character described it is obvious that the circuit on a night-transformer is inoperative during the day-time. This would ordinarily appear objectionable to the customer, and if no compensating advantages were presented it would seein preferable to him that all lights or translating devices should be placed on the circuit which is always alive, thus defeating any attempted saving in core loss. I have therefore found it advisable to charge for current on the all-day circuit at a higher rate than for current on the nightcircuit. The additional expense incident to the use of translating devices on the all-day circuit will thus result in a reduction of the number of such devices to a minimum, thus allowing the use of a smaller transformer for the all-day circuit, which is always operative and in which the transformer core loss is always going on. At the same time a maximum number of translating devices is placed on the night-circuit, thus saving an amount of energy corresponding to the loss which would take place if the circuit were energized during the no-load hours.

The method of charging above described is the direct opposite of the two-rate system now well known, in which current is charged for at lower rates during the day-time, when the station-load is small, than during the night, when it is high. The objects to be obtained in the two systems of metering are different, and therefore not inconsistent. y

The system of metering devised by lne aims to prevent waste of energy in an electrical distribution system, while the principal object sought for by the employment of a multiple-rate system of the ordinary kind is an equalization of load on the system. In the two rate system already mentioned lower rates are charged during the day as an inducement for the customer to use current at the time when the load on the station is small. So far from being inconsistent are these systems that I find it advisable to supply motorloads from the source of supply G during the daytime,while the load on the station is small, and to supply this current at a reduced rate. In the drawings, M illustrates a transformer supplying motors or other translating devices and connected, through a switch s, with the source of supply G. Owing to the reduced rate at which this current is supplied, I nd it advisable in most instances that the circuit should be opened at night, when the motorload or demand for motor-current is a minimum. l f

In connection with the system of distribution described and shown in the drawings I have provided a system of multiple-rate metering which automatically records,according to the predetermined rates, the amount of energy used in both circuits.

In Fig. l I have shown an arrangement suitable for metering at dierent rates the energy expended in the al1-day circuit and the night-circuit. For this purpose a single recording-wattmeter Wis employed, with its current-coils E connected in series with the common return B of the two circuits and its armature connected in shunt across the mains A. B of the all-day circuit, which, as before explained, are always energized. If the electromotive forces of the night-circuit and of the all-day circuit are equal, it will be evident that the energy expended in the two circuits will be metered at the same rate, since a given amount of current iowing in the night-circuit represents the same amount of energy as a like flow of current in the allday circuit. In order, therefore, to cause the wattmeter to register energy in the nightcircuit at a lower rate than in the all-day circuit, I make the two circuits of different electromotive force, that of the nightcircuit being higher than that of the all-day circuit in proportion to the reduction of the rate desired. Thus if it be desired to charge for energy ou the night-circuit at half the rate for that on the day-circuit it is only necessary to make the electromotive force on the night-circuit twice that of the all-day circuit. Under these conditions a given amount of current fiowing in the night-circuit represents twice the expenditure of energy corresponding to the same amount of current in the all- IOO IIO

daycircuit. The Wattmeter, which gives the Same registration for the current in the common return B, regardless from which circuit the current is supplied, consequently registers energy in the night-circuit at half the rate thatit registers energy in the all-day circuit, and this because of the fact that the speed of the meter is proportional to the current in the field-coil. Instead of the form of meter shown any other suitable form of meter may be employed.

In Fig. 2-I have shown a different arrangement for metering energy in the night andin the ail-day circuits at different rates. In this case the two transformers supplying the consumption circuits have the same ratio of transformation, so as to give the same electromotive forces in the two circuits. A single wattmeter W' is employed, as before; but the connections for the same are differently made. The armature of the meter, as in the first instance, is connected across the mains B of the all-day circuit. One of the held-coils or sets ofield-coils F is connected in series with the common return B, While the other fieldcoil F is connected in series with the main A of the all-day circuit. As thus arranged it Will be evident that when current ows in the all-day circuit it Will pass through all of the field-coils of the meter, while when current flows in the night-circuit current will pass only through those coils of the meter which are in series with the common return B. If the turns of the two sets of eldv'coils have an equal effect upon the armature, it will be evident that current in the all-day circuit will be metered at a rate twice thatof the current in the night-circuit. If it be desired to change the relative rates of metering for the two circuits, it is only necessary to change the relative number of turns of the two sets of eld-coils connected, respectively, in series with the common return B and the main A of the all-day circuit. Asvillustrating how this change may be made, I have shown in Fig. 2 the coil F' of the meter as provided with a plurality of terminals t, so that by connecting the main A to different terminals the number of effective turns of the coil F may be varied. The relative rates of metering in the two circuits are approximately in the proportion of the total number of active field-turns to the number of turns in the common return alone. By suitably adjusting this relation of turns the respective rates of metering may be made anything desired.

By the employment of the above-described System of distributing and metering electricity I have found that by far the largest part of the iron losses of the transformers maybe saved, and since this loss constitutes a large percentage of the station output a considerable reduction in price maybe made for those lights which are operative only in the evening. Even with such a reduction in charges the saving effected is generally more than sufficient to compensate for the expense and inconvenience of an additional primary wire.

Although the system of metering which I have described above is particularly useful in connection With alternating-current systems of distribution already described, it will of course be evident that it is in no respect limited thereto, but in its broader features is equally applicable to other systems of distributing current, and I intend hereinafter to lay claim, broadly, to this system of metering regardless of the particular nature of the system of distribution in connection with which it is employed.

I do not claim herein the particular apparat us or combination of apparatus shown and described, but reserve the same for a divisional application, Serial No. 99,618, filed March 24, 1902.,

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent of the United States, is

1. The method of metering the flow of electric energy in a plurality of electric circuits, Which consists in measuring at different rates and simultaneously summing up the flow of energy in the individual circuits.

2. rIhe method of metering the flow of electric energy in two electric circuits which consists in measuring atdifferent rates and simultaneously summing up the flow of energy in the two circuits.

3. The method of recording the consumption of electrical energy, which consists in simultaneously recording at dierent rates the energy consumed in a plurality of electric circuits.

Lt. The method of recording the consumption of electrical energy, which consists in simultaneously recording at different rates the energy consumed in a plurality of interconnected electric circuits.

5. The method of multiple-rate metering, which consists in passing through a single recording-meter the currents from a plurality of circuits in which the energy consumption is to be metered, and causing the meter to sum up and simultaneously record the consumption of energy according to different rates predetermined for the respective cir cuits.

6. The method of multiple-rate metering, which consists in passing through a single recording-meter the currents from a plurality of interconnected circuits in which the energy consumption is to be metered, and causing the meter to sum up and simultaneously record the consumption of .energy according to different rates predetermined for the respective circuits.

In witness whereof I have hereunto set my hand this 3d day of March, 1899.

' CHARLES P. STEINMETZ. Witnesses:

BENJAMIN B. HULL,

MABEL E. JAcoBsoN.

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